1. Field of the Invention
The present invention relates to a method for setting an initial compensation value of a sensor complex module applied to a mobile terminal such as a cellular phone, and more particularly, to a method for setting an initial compensation value of a sensor complex module, which can perform automatic and quick compensation for a gradient error. In the method, the sensor complex module having an acceleration sensor at a main board automatically and quickly measures the gradient error without using a separate measuring controller, thereby improving productivity and convenience in use.
2. Description of the Related Art
A mobile terminal such as a cellular phone provided with an inertial sensor has recently been released. The inertial sensor is packaged for an electrical connection between inside and outside. The inertial sensor is bonded with an electrode of a main board embedded in, for example, a cellular phone using various surface mounting techniques.
Here, the inertial sensor is a sensor used for an inertial navigation system, and measures acceleration and angular velocity and provides information of the acceleration and angular velocity to the system. The inertial sensor may be divided into an accelerometer and a gyroscope. Here, the accelerometer is a sensor that measures the acceleration of an object, and the gyroscope is a sensor that measures the angular velocity of a rotating object.
The inertial sensor is increasingly demanded in general fields including a navigation system of a vehicle, an Internet IV sensor, a shake compensator of a camcorder, besides the cellular phone. Also, the inertial sensor is expected to substitute for an exiting navigation sensor.
Also, the inertial sensor is bonded with a main board of a corresponding device, with a conductive material such as solder interposed therebetween. At the time of bonding, the bonding height may become uneven between right and left or between front and back because of physical influence. For this reason, the sensor is randomly inclined, causing an error in an output value. For example, the output value of the acceleration sensor may increase or decrease in proportion to a gradient, and in such a manner, a terrestrial magnetism sensor also makes an error in an output value.
To solve this problem, the conventional sensor complex module compensates an error by setting an initial compensation value by a method described in FIG. 1. This method will now be described with reference to FIG. 1.
FIG. 1 is a flow chart showing a method for setting an initial compensation value of a conventional sensor complex module. Referring to FIG. 1, the acceleration with respect to three axes (x, y and z) is sensed by using an acceleration sensor (S11), and a maximum value and a minimum value of the sensed acceleration with respect to the three axes are calculated (S12). Then, a sensitivity value is calculated using the maximum and minimum values by Equation 1 below (S13), and an offset value is calculated using the maximum and minimum values by Equation 2 below (S14). Then, the obtained sensitivity and offset values are stored in a memory.Sensitivity value=Maximum value−Minimum value  Equation 1Offset value=(Maximum value−Minimum value/2)=Sensitivity value/2  Equation 2
BY using the sensitivity and the offset value stored and set in the aforementioned manner, the acceleration measured thereafter is compensated.
FIGS. 2(a), 2(b) and 2(c) are views exemplarily showing rotation of a main board for setting an initial compensation value of the conventional sensor complex module. Referring to FIGS. 2(a), 2(b) and 2(c), a separate maximum-minimum measuring unit is needed to set an initial compensation value of the conventional sensor complex module.
As illustrated in FIG. 2(a), a main board with the acceleration sensor is mounted to the maximum-minimum measuring unit. Then, to measure the maximum and minimum values of the acceleration with respect to the three axes, as illustrated in FIGS. 2(b) and 2(c), the maximum-minimum measuring unit to which the main board has been mounted is rotated to 90° with respect to each of the X and Y-axes from the location illustrated in FIG. 2(a), thereby detecting maximum and minimum values of the acceleration with respect to the X, Y and Z axes.
In the method for setting an initial compensation value of the conventional sensor complex module, an error generated by, for example, defective mounting is measured and compensated through such complicated processes using the maximum-minimum measuring device, which makes the error compensation complicated.
Also, an additional measuring movement of a product including therein an acceleration-sensor loaded main board is required, such as rotating or inclining in a certain direction. For this reason, the overload of a manufacturing line may occur, and thus productivity may be lowered.